Posts are primarily deleted for being violent, racist, obscene or for containing content that is sensitive now that we are at war.
If such posts are not deleted, others use them to show how terrible FR and the people who post on it are. Frankly, I'd prefer it if they were left up with a note from the moderator attached that FR rejects their point of view.
But this site is private property. Those who don't like the way it is run have the option of starting their own site which will be run by their rules.
But we both know that deletions go way beyond that. Many are simply for political bias reasons.